Step 3: Spawning
The process of inoculating pasteurized compost with the best quality spawns is called
inoculation or spawning. It is a good idea to have an inoculation room to prepare spawns before
inoculating the substrate bags. If substrate materials are packed in polythene bags, the best
method of spawning is either by using grain spawns or by sawdust spawns. If grain spawns are
used, spawn bottles are gently shaken to separate mushroom seeds (spores) from mycelia.
Thereafter, the bottle is opened carefully and about 2 teaspoon full of spawns is poured into the
substrate bag. Soon after inoculation, both the spawn bottles and the substrate bags are covered.
To ensure even distribution of spawns throughout the inoculated bag, they are slightly tilted
and if sawdust spawns are used, the spawn bottles are broken with an aseptic needle and then a
piece of the spawn is transferred carefully to the substrate bags.
Bulk Spawning
Bulk spawning process is practiced in industrial production of mushrooms. Pasteurized
mushroom compost is mixed with spawns by hands or by using a spawning machine.
Considering the bulk quantities of materials involved, care should be taken to carry out the
spawning process in an environment with an excellent sanitation facility. All personnel
involved in the process are required to be clean; and wear gloves, face mask and head cap.
Inoculation room should have good ventilation but air must be filtered, preferably with a High
Efficiency Particulate Air (HEPA) filter. After mixing the mushroom compost with the spawns,
they are placed in the growing containers and then the containers are covered. Spawn rate required to inoculate a batch of mushroom compost is often expressed on the basis of spawn
weight versus compost weight; a 2 percent spawning rate is considered to be optimum.
Spawn Run
Soon after the inoculation process, the spawned substrate bags are transported into dark
mushroom production chambers or mushroom houses. Soon the fungal spores begin to grow
and multiply, taking food from substrate materials. The period between the beginning of fungal
mycelia growth and the covering of the entire substrate with white-colored mycelium is known
as spawn run period and the process is called spawn run. Normally in 15 to 25 days, the entire
substrate appears white.
During spawn run period, tremendous heat is generated due to the enhanced biological
activity of the growing fungal mycelia and as a result, the compost temperature increases up to
85°F, depending on the type of the mushrooms. This heat build-up adversely affects the growth
of the mushrooms as well as the quality of the crop. Therefore it is necessary to maintain proper
temperature and moisture content during the entire spawn run period of mushroom growing.
During spawn run, both oxygen and carbon dioxide are required for mycelia growth. Excess
water should not be present in the substrate. For this, make sure that sufficient drainage holes
are provided in the growing containers. As mycelia grow in number, more oxygen may be
required by them; so large holes may be provided on the top of the containers to allow more
aeration. Optimum temperature that is to be maintained during spawn run is between 15 and 20°C. There should be adequate ventilation but light is not required.